In projectors with light modulator illumination devices, which are often also called digital projectors, the light modulator can be illuminated time-sequentially with light of different colours from the different wavelength ranges in order to generate, time-sequentially, coloured partial images which are then perceptible to an observer only in temporal superimposition as a multi-coloured image. In order to generate, time-sequentially, the different colours, for example a colour wheel with a first filter surface which is rotatable about an axis can be provided, wherein the first filter surface comprises at least three surface segments arranged one behind the other in the direction of rotation which, when the first filter surface is rotated, protrude successively into an illumination beam path from a multi-coloured light source to the light modulator. The light modulator can thus be illuminated with the different colours successively by rotating the colour wheel.
Such digital projectors can be used e.g. for flight simulators. Here it is desired to be able to also project an infrared image at the same time as the multi-coloured image visible to the human eye, in order thus to be able e.g. to train for the use of night vision devices. It is known from U.S. Pat. No. 8,382,297 B2 to provide a special colour wheel for this which, in addition to the at least three surface segments arranged one behind the other for wavelengths from the visible wavelength range, comprises at least one more surface segment for wavelengths from the infrared range, with the result that an infrared illumination of the light modulator can also be carried out time-sequentially when the colour wheel is rotated. However, this is laborious as the colour wheel has to be changed accordingly. The control of the colour wheel and of the light modulator is also changed in this case as an additional surface segment is provided in the colour wheel. In addition, the light output for the visible image is reduced, even if no infrared image is to be projected, as the colour wheel always comprises the surface segment for the infrared range.